Preparation of a polysaccharide adjuvant and its application in the production of a foot-and-mouth disease virus-like particles vaccine

Foot-and-mouth disease (FMD) virus-like particles (VLPs) comprise a new and effective FMD vaccine, which often requires the addition of adjuvants to induce a vigorous immune response in order to protect livestock from the challenge of FMD virus (FMDV). Oil emulsion delivery systems have been developed and used widely in the field of veterinary vaccines because of their low cost, slow release, and efficient antigen protection. In this study, we designed and synthesized an optimized Achyranthes bidentata polysaccharide (ABP) delivery system (ABPOA) based on a pseudo-ternary phase diagram. We systematically evaluated the stability, biocompatibility, and immunological effects of the ABP delivery system. The results demonstrated that ABPOA is a stable adjuvant delivery system and capable of long-term storage at 37 degrees C for up to 6 months. ABP-VLPs can be effectively stored for long periods when ABPOA is used as the delivery system for VLPs. Importantly, guinea pig-specific antibodies were significantly increased within 28 days when ABPOA was used as a delivery system, thereby promoting the proliferation of splenic lymphocytes. In addition, immunization with one dose of ABP-VLPs resulted in complete protection from homologous FMDV challenge in guinea pigs. Therefore, the polysaccharide oil emulsion adjuvant comprising ABPOA effectively improved the immunogenicity of FMD-VLPs. These findings provide a theoretical basis for the preparation of oil emulsion adjuvants for veterinary vaccines.